Question: When shall we call you? In Exercise, we learned of a study that dialed telephone numbers at random during two periods of the day. Of 2304 numbers called on weekday mornings, 1313 answered. Of 2454 calls on weekday evenings, 1840 were answered.
(a) Make a two-way table of time of day versus answered or not. What percentage of calls were answered in each time period?
(b) It should be obvious that there is a highly significant relationship between time of day and answering. Why?
(c) Nonetheless, carry out the chi-square test. What do you conclude?
Exercise: When shall we call you? As you might guess, telephone sample surveys get better response rates during the evening than during the weekday daytime. One study called 2304 randomly chosen telephone numbers on weekday mornings. Of these, 1313 calls were answered and only 207 resulted in interviews. Of 2454 calls on weekday evenings, 1840 were answered and 712 interviews resulted. Give two 95% confidence intervals, for the proportions of all calls that are answered on weekday mornings and on weekday evenings. Are you confident that the proportion is higher in the evening?